Environmental awareness has prompted numerous efforts to reduce the escape of gasoline fumes and liquid into the atmosphere, as from vehicle fuel tanks, particularly when filling the tank with fuel. Attention is now being given to fuel filling stations where self-service is now more common than service by gas station attendants. Customer self-service in the vehicle fuel tank filling operation aggravates the air pollution problems already associated with vehicle gasoline tank filler necks, which of course must be left open with the associated outside gas cap removed during tank filling. Excessive tank open time often results from improper customer operation of the fuel pump hose nozzle, such as leaving the same in the fill tube longer than necessary for tank filling while the gas cap is off and hence the tank is open via the filler neck to ambient atmosphere. Fuel splash back from the tank into and up out of the filler neck to ambient atmosphere as the tank approaches full level is also aggravated by amateur customer self-service.